Safety switch



1961 F. w. MURPHY 3,01

SAFETY SWITCH Filed Nov. 30, 1959 IN VENTOR BY 4%- MM ATTORNEYS United States Patent 3,012,113 SAFETY SWITCH Frank W. Murphy, 5328 E. Admiral Place, Tulsa, Okla. Filed Nov. 30, 1959, Ser. No. 856,102 2Claims. (Cl.200-56) This invention relates to a safety switch, and comprises an improvement over my previous Patent No. 2,722,576, dated November 1, 1955.

A primary object of this invention is the provision in a water pressure safety switch of an adjustable lockout. As conducive to a clearer understanding of this invention, it may be here pointed out that when an irrigation pump pushes water up a river bank or over a hill, the static head of water in the pipe going uphill measures much higher than highest contact settings available on the standard pressure switch. By virtue of the instant invention, a predetermined selected shut down setting for any irrigation or contractor pump, regardless of static head, may be provided, which will thus prevent pumps running dry, water wasting out on the field, or serious erosion when couplings part.

An additional object of the invention is the provision of such a device provided with an adjustment nut having a lockout range covering 50% of the scale.

Still another object of the invention is the provision of a lockout push button which locks the point of contact out of position with shut down contact for starting.

Still another object of the invention is the provision of such a device which is sturdy and durable in construction, reliable and eflicient in operation, and relatively simple and inexpensive to manufacture, assemble and utilize.

Still other objects will in part be obvious and in part be pointed out as the description of the invention proceeds, and shown in the accompanying drawings wherein there is disclosed a preferred embodiment of this inventive concept.

In the drawing:

FIGURE 1 is a front elevational view of one form of switch embodying features of the instant invention, the connections thereof being illustrated schematically;

FIGURE 2 is an enlarged view similar to FIGURE 1, but partially broken away,.showing the parts in a different position of adjustment;

FIGURE 3 is an enlarged fragmentary detail perspective view of a constructional element; and

FIGURE 4 is a sectional view taken substantially along the line 4-4 of FIGURE 3, as viewed in the direction indicated by the arrows.

Having reference now to the drawings in detail, there is generally indicated at 1.0 a switch embodying the instant invention, which includes a casing 11 having a scale 12 thereon, and a movable contact pointer arm 13 pivotally mounted as on a pivot 14. A connection 15 is associated with the pointer 13, and may lead to ground.

An adjustable micrometer contact is generally indicated at 16, and includes an internally threaded sleeve 17 which extends through the side wall of the casing 11. The sleeve 17 is also externally threaded, as at 18, to permit its engagement with a correspondingly threaded aperture in the side wall of the casing.

Extending through the sleeve 17 is a contact screw 19, upon which is positioned a pair of clamping nuts 20,

. which are adapted for the engagement of a contact wire 21, which may lead from any desired instrument. Obviously, when the pointer is in the position disclosed in FIG- URE 2, a circuit is closed between the wires 15 and 21, and when the pointer is in the position shown in FIGURE 1, such circuit is broken. Theposition of the pointer 13 may be governed by any predetermined desired pressure or derivative thereof, such as in the illustrative embodiment herein shown and described water pressure in an irrigation pipe.

The adjustable lockout feature of the instant invention is comprised of an L-shaped bracket, generally indicated at 25, having a pair of spaced apart ears 26. Between the ears 26 there are positioned a pair of opposed ears 27, which comprise integral portions of an L-shaped detent member including a shank 28, a forwardly projecting portion 29, and an oifset contact engaging portion 36. A pin or axle 31 extends through suitable aligned apertures in the ears 26 and 27, and a coil spring 32 surrounding the pin 31 serves normally to bias the inclined portion 39 toward engagement with an associated notch 13A in the contact pointer 13. The L- shaped bracket 25 has integrally aflixed thereto a stud thread 35, which extends through an unthreaded opening in the side wall of the casing 11 and exteriorly thereof. A lockout push button member 36 is freely slidable in the internal bore 37 of the stud 35, and is provided interiorly of the casing 11 with an enlarged head 38 which is adapted to engage the portion 23 to bias the angularly disposed member, upon inward pressure of the push button 36 out of engagement with its associated notch 13A to permit the contact pointer 13- to move into engagement with its associated contact screw 19 to close the circuit to the pump or other appliance with which the switch is used.

A coil spring 40 positioned in the bore 37 engages at one end against the inner side of the head 38, and at its other end against a shoulder 41 formed by a reduction in the size of the member 36 interiorly of the bore 37. The spring 40 serves normally to bias the push button 36 to retracted or extended position out of engagement with the member 28.

A nut 45 is threaded upon stud 35, and an arm 46 has an angular offset portion 47 which engages about the flat portion 48 of the stud toprevent rotation of the latter. A screw 49 passes through the outer end of arm 46 and presses flat portion 48 thereof against nut 45. It will be understood from the structure just outlined that rotation of nut 45 will shift stud 35 axially to set L-shaped bracket 25 and its associated lockout assembly in a selected position relative to the pointer arm.

Obviously, when it is desired to vary the adjustment, the screw 49 may be loosened, which permits the adjustment of nut 45, which in turn varies the position of L-shaped bracket 25 and its associated mechanism, and, consequently, varies the pressure at which the lockout member 30 may be disengaged from the notch 13A of contact pointer 13 to permit contact arm 13' to moveinto engagement with screw contact 19 to close the circuit to start the pump or other mechanism with which the device is associated.

From the foregoing it will now be seen that there is herein provided a device which accomplishes all of the objects of this invention, and others, including many advantages of great practical utility and commercial importance.

As many embodiments may be made of this inventive concept, and as many modifications may be made in the embodiments hereinbefore shown and described, it is to be understood that all matter herein is to be interpreted merely as illustrative and not in a limiting sense.

What is claimed is:

1. A fluid pressure operated switch including an adjustably fixed contact and a movable contact comprising a fluid pressure operated pivoted pointer arm, a lockout for said arm including a push button and pivoted latch member adapted to be swung by said push button to a position to restrain further movement of said pivoted arm, a threaded stud extending through an unthreaded opening in a support for mounting said pivot latch, the outer end position of said stud having a non-circular portion, a nut threaded on said stud and abutting said support to fixedly position said stud axially and thereby position said lockout with relation to said pointer arm, an arm having one end fitted to said noncircular portion of said stud and engaging said nut, means at the opposite end of said arm for pressing arm and nut against said support with said nut adjusted to position said lockout at a selected adjustment. I

2. The apparatus of claim 1 wherein said lockout includes an L-shaped bracket, one leg of said bracket defining spaced parallel ears, and said latch includes spaced ears pivoted between the ears of said bracket, a latch finger for engagement with said pointer arm, and a coil spring between said ears of said bracket for biasing said finger toward said push button.

References Cited in the file of this patent UNITED STATES PATENTS 423,441 Putman Mar. 18, 1890 10 918,778 Schwering Apr. 20, 1909- 2,165,699 Fisher July 11, 1939 2,722,576 Murphy et a1. Nov. 1, 1955 

